Differences In Relative Composition Research Articles

Towards realism in hazard assessment of plastic and rubber leachates – Methodological considerations

While plastic chemicals are key drivers of observed effects to aquatic species, there remains a lack of standardized and fit-for-purpose approaches for experimentally deconvoluting the effects of plastic chemicals from particle effects. This study investigated differences in chemical composition determined using two different organic solvents for extractions (dichloromethane-ethyl acetate, methanol) and by thermal desorption applied to 51 thermoplastic and elastomer products. The composition of natural water leachates of four select elastomers was also investigated. The number of chemical features in each material varied according to the extraction method, with solvent extracts exhibiting the most chemicals, and only 19 compounds commonly identified by all three methods. The number of chemical features in leachates was generally similar to the corresponding chemical extracts, but strong differences in relative composition were detected. While turbulence had minimal impact on leachate composition, particle loading strongly influenced leachate composition, temperature and salinity influenced the leachate concentration for some chemicals, and leaching time depended upon chemical mobility. Leachate composition cannot be readily predicted from particle characterization and multiple parameters are drivers of compositional variance in aquatic leachates. Recommendations for performing leaching studies that are relevant for hazard characterization in a realistic aquatic environment risk assessment scenario are suggested, with a particular focus on particle loading.

Floral resource partitioning by individuals within generalised hoverfly pollination networks revealed by DNA metabarcoding

Pollination is a key ecosystem service for agriculture and wider ecosystem function. However, most pollination studies focus on Hymenoptera, with hoverflies (Syrphidae) frequently treated as a single functional group. We tested this assumption by investigating pollen carried by eleven species of hoverfly in five genera, Cheilosia, Eristalis, Rhingia, Sericomyia and Volucella, using DNA metabarcoding. Hoverflies carried pollen from 59 plant taxa, suggesting they visit a wider number of plant species than previously appreciated. Most pollen recorded came from plant taxa frequently found at our study sites, predominantly Apiaceae, Cardueae, Calluna vulgaris, Rubus fruticosus agg., and Succisa pratensis, with hoverflies transporting pollen from 40% of entomophilous plant species present. Overall pollen transport network structures were generalised, similar to other pollination networks elsewhere. All hoverfly species were also generalised with few exclusive plant/hoverfly interactions. However, using the Jaccard Index, we found significant differences in the relative composition of pollen loads between hoverfly genera, except for Volucella, demonstrating some degree of functional complementarity. Eristalis and Sericomyia species had significant differences in relative pollen load composition compared to congeners. Our results demonstrate the range of pollens transported by hoverflies and the potential pollination function undertaken within this ecologically and morphologically diverse guild.

Quantitative compositional analysis of InxGa1−xN/GaN multiquantum wells in light-emitting diodes

Abstract

Fatty acid and stable isotope characteristics of sea ice and pelagic particulate organic matter in the Bering Sea: tools for estimating sea ice algal contribution to Arctic food web production

We determined fatty acid (FA) profiles and carbon stable isotopic composition of individual FAs (δ(13)CFA values) from sea ice particulate organic matter (i-POM) and pelagic POM (p-POM) in the Bering Sea during maximum ice extent, ice melt, and ice-free conditions in 2010. Based on FA biomarkers, differences in relative composition of diatoms, dinoflagellates, and bacteria were inferred for i-POM versus p-POM and for seasonal succession stages in p-POM. Proportions of diatom markers were higher in i-POM (16:4n-1, 6.6-8.7%; 20:5n-3, 19.6-25.9%) than in p-POM (16:4n-1, 1.2-4.0%; 20:5n-3, 5.5-14.0%). The dinoflagellate marker 22:6n-3/20:5n-3 was highest in p-POM. Bacterial FA concentration was higher in the bottom 1 cm of sea ice (14-245 μg L(-1)) than in the water column (0.6-1.7 μg L(-1)). Many i-POM δ(13)C(FA) values were higher (up to ~10‰) than those of p-POM, and i-POM δ(13)C(FA) values increased with day length. The higher i-POM δ(13)C(FA) values are most likely related to the reduced dissolved inorganic carbon (DIC) availability within the semi-closed sea ice brine channel system. Based on a modified Rayleigh equation, the fraction of sea ice DIC fixed in i-POM ranged from 12 to 73%, implying that carbon was not limiting for primary productivity in the sympagic habitat. These differences in FA composition and δ(13)C(FA) values between i-POM and p-POM will aid efforts to track the proportional contribution of sea ice algal carbon to higher trophic levels in the Bering Sea and likely other Arctic seas.

Comparison of Parameters Characterizing Organic Matter in a Combined Sewer During Rainfall Events and Dry Weather

To understand the effect of combined sewer overflows on the river Seine (France), a characterization of effluent in terms of organic matter and bacterial biomass was carried out during several sampling campaigns performed in a combined sewer located in Parisian suburbs under wet and dry weather conditions. Measurements classically used to study wastewater (suspended matter, chemical oxygen demand [COD] and biochemical oxygen demand [BOD]) were compared with the estimate of biodegradable and refractory fractions of particulate and dissolved organic carbon. Relationships among different parameters used to describe organic material in effluent were established. Even for large fluctuations in organic matter concentrations, highly homogeneous ratios between the different descriptors during wet and dry weather were observed, and no significant differences could be observed in two catchments strongly differing by their sizes. The only two small differences in relative composition that could be observed between dry and wet weather were slightly lower content of organic carbon in suspended solids and a lower biodegradability of this material during rain events. Accordingly, with the help of obtained relationships and values of classical variables like turbidity, BOD, and COD for a given effluent, it is possible to make reasonably accurate estimates of its composition in terms of biodegradable and refractory fractions of dissolved and particulate organic matter and bacterial biomass.

Volatile organic compound emissions from flowers of the most occuring and economically important species of fruit trees

Six agriculturally important fruit species were screened for emissions of isoprene and other volatile organic compounds (VOCs) at full bloom. The air from a Teflon growth chamber containing the tested plants was collected on carbon absorbents and analyzed by thermal desorption gas chromatography and mass spectrometry (TD-GC-MS). Over 80 individual compounds were identified. All the screened species were isoprene emitters and revealed a unique fingerprint profile determined by monoterpenes. Differences in relative composition of monoterpenes occurred mainly between pome and stone fruit plants. Linalool was emitted exclusively by apple and pear flowers, whereas apricot, cherry and plum showed a pattern dominated by α-pinene and to a less extent by camphene. Limonene appeared to be the most abundant emitted compound from peach flowers. Preliminary quantification of monoterpene emissions indicated that, at full bloom, cherry was the major emitter and peach the minor one.

Differences in the carbon composition of source profiles for diesel- and gasoline-powered vehicles

Abstract Filter samples of diesel-fueled heavy-duty and gasoline-fueled light-duty vehicle exhaust were acquired under controlled conditions associated with the State of Arizona's motor vehicle inspection and maintenance program. Samples of a mixture of emissions from these vehicles were also acquired at roadside sites. These samples were analysed for mass, elements, ions, and carbon. The carbon which evolved at temperatures of 120, 250, 450, and 550 C in a pure helium atmosphere, and at temperatures of 550, 700, and 800 C in a 2°0 oxygen 98°0 helium (by volume) atmosphere was measured with a flame ionization detector. The fraction of carbon which evolved at 700 C in the 2°0 oxygen atmosphere was found to be nearly 10-times as abundant (as a fraction of PM2.5 mass emissions) in the heavy-duty diesel-fueled vehicle emissions relative to the light-duty gasoline-fueled vehicle emissions. The organic carbon which evolved at 120 C was twice as abundant in diesel exhaust. The fraction of carbon which evolved at 550 C in an oxidizing atmosphere was twice as abundant in gasoline-fueled vehicle exhaust as it was in diesel exhaust. These differences in relative composition may be sufficient to allow diesel- and gasoline-fueled vehicle exhaust contributions to be distinguished from each other in ambient samples through the use of receptor models.

Halothane genotype by weight interactions on lean yield from pork carcasses

Data on 42 halothane-sensitive pigs (HSL, nn-genotype), 169 Lacombe pigs (LAC, NN-genotype), 41 crossbred pigs (XBD, Nn-genotype), and 72 Yorkshire pigs (YRK, NN-genotype) representing 145 gilts and 179 castrates, were obtained over the liveweight range from 74.0 to 134.5 kg (average 105 kg) to examine the effect of genotype, gender and slaughter weight on the composition of the four lean cuts (ham, loin, picnic and butt). Gilts had a greater proportion of dissectible lean from lean cuts than castrates (557 ± 2.8 vs. 525 ± 2.6 g kg−1). The HSL pigs had the highest and LAC pigs the lowest commercial dressing percentage, increasing respectively from 85.3 to 86.0% and 79.7 kg to 82.6% as slaughter weight increased from 80 to 130 kg. Corresponding figures for XBD and YRK pigs, were 82.5 to 85.4 and 80.6 to 84.6%, respectively. Dissectible lean from lean cuts from 65-kg carcasses was 606, 525, 536 and 575 g kg−1 for HSL, XBD, LAC and YRK pigs, respectively. Corresponding figures for 85-kg and 105-kg carcasses were 574, 525, 515, and 555 g kg−1 and 542, 525, 494, and 535 g kg−1, respectively from HSL, XBD, LAC and YRK pigs. LAC and YRK pigs, each with exclusively NN-genotypes but differing in composition of lean cuts, maintained their relative differences in composition over the weight range studied. Heterogeneity of slopes for changes in proportion of lean in the lean cuts with increasing weight among the HSL, XBD and LAC pigs implied a genotype × weight interaction that could best by explained by an apparent increase in the dominance of the halothane gene with increasing carcass weight. Key words: Swine, carcass composition, halothane gene, weight, Lacombe, Yorkshire

Multicomponent spectra from 31P-NMR studies of the phase equilibria in the system dioleogylphosphatidylcholine-dioleoylphosphatidylthanolamine-water

The phase equilibria in mixtures of dioleoylphosphatidylcholine (DOPC), dioleoylphosphatidylethanolamine (DOPE) and water were studied by 31P-NMR and 2H-NMR. The chemical shift anisotropy is greater for DOPC than for DOPE (6–9 ppm in the lamellar phase). This difference can most probably be ascribed to different order parameters for the two lipid head groups. 31P-NMR spectra recorded from a lamellar phase formed by DOPC-DOPE-water below maximum hydration exhibit two resolved, superimposed powder spectra. The chemical shift anisotropy for both phospholipids has greater values at excess water contents than below maximum hydration, and the spectral resolution between DOPC and DOPE in the lamellar phase is strikingly diminished at excess water contents. From 31P-NMR spectra it is possible to observe relative differences in composition between different lipid phase existing in equilibrium. The proportion of DOPE is decreased in the lamellar phase, and is increased in the reversed hexagonal phase, when these phases exist in equilibrium.

In Vitro Effects of Skin Lipid Extracts on Skin Bacteria in Relation to Age and Acne Changes

Skin lipid extracts of 185 persons of different age were tested in vitro against single representatives of skin bacteria: Staphylococcus aureus, S. epidermidis, Propionibacterium acnes, P. granulosum and Corynebacterium sp. in order to find differences in their inhibitory effects. Percentages of the extracts inhibiting the first 4 bacteria were nearly the same (about 20%) while corynebacteria were inhibited by only 3 extracts. Extracts showing these properties were isolated mainly from adolescents with acne changes, young adults, about 20 yr old, and from children 8--10 yr old, but not from elderly people. The age-related differences in growth inhibition may be related to known differences in relative composition of the sebum constituents according to age. Forty-two extracts of acne patients and healthy adults and adolescents showed an inverse effect in vitro: they enhanced bacterial growth. Growth enhancement was demonstrated only for P. granulosum.

Food of Two Cohabiting Tide-Pool Cottidae

The organisms found on seven dates in the stomachs of two cottids (Oligocottus maculosus and O. snyderi) cohabiting four rocky tide pools on the west coast of Vancouver Island were the same except for one minor item. Quantitatively, a number of differences were present. For the major food items, the interspecific differences in relative composition of the diets were greatest for amphipods and copepods. Lesser differences are seen for annelids, isopods, and chironomid larvae. However, these were more likely a reflection of differences in microhabitat and behavior rather than interspecific competition for food.

陸水のNa, Cl及びNa/Clに就て

1. In view of the fact that precipitation constitutes the primary source of the salt of inland waters, comparison was made between sea water and rain and snow for major salt components in order to discuss the cause of difference in relative composition between these two different categories of water.2. The next step was to compare rain and snow, and inland waters, whereby possible factors contributing to the deviation of the concentrations of Na and Cl and the ratio Na/Cl in inland waters from those in rain and snow were made clear. As such factors, dissolution of windborne salt, erosion of rock and soil materials, addition of mineral and thermal spring waters, agriculturally used chloride manure, sodium chloride waste from domestic life including excreta, sodium and chloride contained in mine and other industrial wastes were considered. Climatic factors were also to be considered, and among them annual averages of regional temperatures are especially important in relation to evaporation and soil erosion. Furthermore, annual precipitation is one of the fundamental factors.3. The magnitude of contribution by some of these factors to the Japanese inland waters was estimated by using the data available. The data for rain and snow were from the author's own laboratory, those for river waters from J. KOBAYASHI and those for ground water from S. OANA'S laboratory, Institute of Earth Sciences, Nagoya University.4. The conclusion is : a). In comparison with the waters in the regions facing the Pacific Ocean, those in the regions facing the the Japan Sea are enriched by Na and Cl with a low Na/Cl. The strong winter monsoon from Siberian air mass transports sea spray from the Japan Sea into the regions facing that sea, where the spray falls down in the forms of snow and rain.b). Geologically speaking, the Japanese inland waters are categorized into three fundamental types : volcanic material type, granitic material type and sedimentary rock type.The waters of Hokkaido, the northernmost island, and the Tohoku District, the northernmost region of Honshu, the Main Island of Japan, represent the volcanic material type and are characterized by high contents in Na, Mg, Cl, SO4and SiO2 with a low Na/Cl. The waters of the Kyushu District, the southernmost among the four large islands constituting Japan, are also of volcanic material type. The waters, however, are characterized by less enrichment of chloride with a higher Na/Cl.The waters of the Chugoku District, the southwestern part of Honshu, where granite is dominant, represent the granitic material type characterized by a low salinity. It is evident that rocks of granite type are less soluble than other types of rocks such as sedimentary or volcanic.The characteristic of sedimentary rock type water is richness in Ca. There is no calcite area extensive enough to form a special district representing this type of water. The waters of the Kanto District with Tokyo on its verge are of composite nature of two water types, volcanic and sedimentary rock.5. Finally, the ratio Na/Cl of inland waters was reviewed world-wide, and explanations were given to unusually low Na/Cl for some Antarctic waters and the water of the Dead Sea.